Wireless communication system, wireless communication setting method, base station, mobile station, and program

ABSTRACT

A base station includes a transmitter configured to transmit a downlink control information to a user equipment, the downlink control information being generated based on one of (1) a first uplink allocation information indicating a first frequency block corresponding to a first plurality of subcarriers which are contiguous in frequency and (2) a second uplink allocation information indicating a second frequency block corresponding to a second plurality of subcarriers which are contiguous in frequency and a third frequency block corresponding to a third plurality of subcarriers which are contiguous in frequency, the second frequency block and the third frequency block being separated in frequency.

TECHNICAL FIELD

The present invention relates to a mobile wireless system, and a settingmethod for wireless communications.

BACKGROUND ART

To fulfill requirements of speedup in mobile wireless communications,broadband wireless communications become essential. In broadband mobilewireless communications, influence of a plurality of delay paths causesfrequency selective phasing to arise on a frequency axis, with whichchannel quality (or Channel Quality Indicator: CQI) varies. Moreover,when considering multiple access in which a base station communicateswith a plurality of mobile stations (also referred to as UserEquipments: UE's), the mobile stations communicate with the base stationin different environments, so that CQI in the frequency domain isdifferent from mobile station to mobile station. Thus, it has been knownthat system throughput is improved by making scheduling comprisingcomparing CQI in the frequency domain for a mobile station with eachother, and allocating a sub-carrier with excellent CQI to each mobilestation. Such scheduling is generally referred to as channel-dependentfrequency scheduling or frequency domain channel-dependent scheduling.

According to Long Term Evolution (LTE) being currently standardized inthe 3rd Generation Partnership Project (3GPP), Orthogonal FrequencyDivision Multiplexing (OFDM) is adopted for a downlink access scheme.The aforementioned channel-dependent frequency scheduling is applied toan LTE downlink, and a plurality of frequency blocks can be allocatedper mobile station, where a frequency block is composed of resourceblocks (each of which is composed of a plurality of sub-carriers) thatare consecutive on the frequency axis within one transmit time Interval(TTI). FIG. 17 shows an example of frequency block allocation in an LTEdownlink. This represents a case in which four mobile stations arescheduled within one TTI in a system band. The frequency block count formobile station 1 (UE1) is three, the frequency block count for mobilestation 2 (UE2) is two, the frequency block for mobile station 3 (UE3)counts two, and the frequency block for mobile station 4 (UE4) countsone.

On the other hand, for an access scheme in an LTE uplink, SingleCarrier-Frequency Division Multiplexing Access (SC-FDMA) is adopted(which is also referred to as Discrete Fourier Transform-spread-OFDM(DFT-s-OFDM) in a transmitter configuration for sub-carrier mapping inthe frequency domain.) In an LTE uplink, again, channel-dependentfrequency scheduling is applied; however, to hold the Peak to AveragePower Ratio (PAPR) down to a smaller value, a limit is placed inallocating consecutive resource blocks per mobile station within oneTTI. This means that the frequency block count is always one. FIG. 18shows an example of frequency block allocation in an LTE uplink. As withFIG. 17, this represents a case in which four mobile stations arescheduled within one TTI in a system band. The frequency block count forany one of mobile stations 1-4 (UE1-UE4) is always one.

Non-patent Document 1 has proposed contemplation of improvement ofsystem throughput by adopting an access scheme (which will be sometimesreferred to as Multi-Carrier FDMA (MC-FDMA) hereinbelow), which allowsallocation of a plurality of frequency blocks per mobile station withinone TTI, as an extended version of SC-FDMA, to enhance a multi-diversityeffect in frequency scheduling. It should be noted that theMulti-Carrier FDMA (MC-FDMA) is a scheme sometimes referred to asFDMA-Adaptive Spectrum Allocation (FDMA-ASA).

FIG. 19 shows exemplary SC-FDMA and MC-FDMA transmitter configurations,and their spectra. The block configurations in the SC-FDMA and MC-FDMAtransmitters are the same, which is comprised of a data generatingsection 1701, a DFT section 1702, a sub-carrier mapping section 1703, anIFFT (Inverse Fast Fourier Transform) section 1704, and a cyclic prefixsection 1705.

First, data production is performed in the data generating section 1701,and signals in the time domain are transformed into those in thefrequency domain at the DFT section 1702, which are then supplied to thesub-carrier mapping section 1703 as input. A difference between SC-FDMAand MC-FDMA is the limit of the frequency block count in mappingsub-carriers in the sub-carrier mapping section. While the frequencyspectrum is always continuous in SC-FDMA (frequency block count=1), itmay be discrete in MC-FDMA (frequency block count>1). Next, at the IFFTsection 1704, the signals in the frequency domain is transformed intothose in the time domain, which are then added with a cyclic prefix, andtransmitted. Cyclic prefix addition refers to an operation of copying atail of data to a head of a block, as shown in FIG. 20. The cyclicprefix is inserted for the purpose of effectively implementing frequencydomain equalization on the receiver side. The length of the cyclicprefix is desirably set such that the maximum delay time of delay pathsin the channel is not exceeded.

Moreover, PAPR in OFDM increases as the number of sub-carriers becomeslarger. However, an increase of PAPR is significantly reduced for anumber of sub-carriers of the order of 50, at which PAPR is almostsaturated. In broadband transmission in which the multi-user diversityeffect can be expected, the number of sub-carriers is usually greaterthan 50, in which case improvement of PAPR cannot be expected even witha smaller frequency block count. On the other hand, since in MC-FDMA, afrequency spectrum that is discrete on the frequency axis is introducedfor a larger frequency block count, resulting in higher PAPR. Therefore,improvement of PAPR can be expected by holding the frequency block countdown to a smaller value in MC-FDMA.

By increasing the frequency block count, the degree of freedom inallocating resource blocks becomes higher, and the multi-diversityeffect in channel-dependent frequency scheduling is enhanced. However,when the frequency block count is increased, the overhead due tonotification of information on resource block allocation may be greater.In fact, a bitmap method (a notification method suitable for a largerfrequency block count), which is currently being studied for adoption innotification of information on resource block allocation in an LTEdownlink (see Non-patent Documents 2, 3), has a greater overhead thanthat in a tree-based method (a notification method suitable for asmaller frequency'block count) for use in notification of information onresource block allocation in an LTE uplink (see Non-patent Document 4).

In particular, in a case that 100 resource blocks are to be allocated,100-bit scheduling information is required in using the bitmap method,whereas log₂ 100 (100+1)/2=13-bit scheduling information is requiredusing the tree-based method (for frequency block=1). In practice, in anLTE downlink, a limit is imposed on the resource blocks to be allocatedsuch that a maximum of 37-bit of scheduling information is used.Moreover, when the tree-based method is applied to a case with a largerfrequency block count, a required number of bits in notification is(frequency block count) times larger than that in SC-FDMA in which thefrequency block count is one. In particular, assuming that the overheadin using the tree-based method for frequency block count=1 is 13 bit asdescribed above, the overhead is increased such as 13×2=26 bits forfrequency block count=2, or 13×4=52 bits for frequency block count=4.

Non-patent Document 1: “A Study on Broadband Single Carrier TransmissionTechnique using Dynamic Spectrum Control” by Keigo MASHIMA and SeiichiSAMPEI, Technical Report of IEICE, RCS2006-233, January 2007

Non-patent Document 2: 3GPP R1-074208, LG Electronics, “DL LVRBallocation approach 2,” October 2007

Non-patent Document 3: 3GPP R1-072723, Mitsubishi Electric, “SchedulingPolicy and Signaling way on DL Resource Allocation,” June 2007

Non-patent Document 4: 3GPP R1-070881, NEC Group, NTT DoCoMo, “UplinkResource Allocation for E-UTRA,” February 2007

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

As described above, since the number of patterns of resource blockallocation is generally increased by increasing the frequency blockcount, the overhead due to scheduling information to be notified by abase station to a mobile station becomes higher. Therefore, themulti-diversity effect and the overhead due to scheduling informationare in a tradeoff relationship. FIG. 21 is a system diagram of atechnique relating to the present invention. The technique uses the sameand fixed frequency block count for all mobile stations. Therefore,optimization taking account of the tradeoff between the multi-diversityeffect and the scheduling overhead is not fully achieved.

Moreover, although it has been known that PAPR is dependent upon thefrequency block count in an access scheme of MC-FDMA, the same and fixedfrequency block count is nevertheless used for all mobile stations.Thus, the frequency block count is not set or updated taking account ofPAPR.

For the reasons above, there is a problem that the achievable throughputis limited.

An object of the present invention is to provide techniques of settingthe frequency block count taking account of the tradeoff between themulti-user diversity effect and the overhead due to schedulinginformation.

Means for Solving the Problems

The present invention for solving the problems described above is awireless communication system, characterized in comprising a settingunit for setting the number of resource block groups, each of which isconstructed of at least one or more consecutive resource blocks on afrequency axis.

The present invention for solving the problems described above is amobile station, characterized in comprising a setting unit for settingthe number of resource block groups, each of which is comprised of atleast one or more consecutive resource blocks on a frequency axis.

The present invention for solving the problems described above is amobile station, characterized in that said mobile station transmits datasignals using resource blocks allocated by a base station so that thenumber of resource block groups, each of which is comprised of at leastone or more consecutive resource blocks on a frequency axis, is equal toor smaller than a set value.

The present invention for solving the problems described above is a basestation, characterized in comprising a setting unit for setting thenumber of resource block groups, each of which is comprised of at leastone or more consecutive resource blocks on a frequency axis.

The present invention for solving the problems described above is asetting method for wireless communications, characterized in comprisingsetting the number of resource block groups, each of which is comprisedof at least one or more consecutive resource blocks on a frequency axis.

The present invention for solving the problems described above is aprogram, characterized in causing a mobile station to execute settingprocessing of setting the number of resource block groups, each of whichis comprised of at least one or more consecutive resource blocks on afrequency axis.

The present invention for solving the problems described above is aprogram, characterized in causing a mobile station to execute theprocessing of transmitting data signals using resource blocks allocatedby a base station so that the number of resource block groups, each ofwhich is comprised of at least one or more consecutive resource blockson a frequency axis, is equal to or smaller than a set value.

The present invention for solving the problems described above is aprogram, characterized in causing a base station to execute settingprocessing of setting the number of resource block groups, each of whichis comprised of at least one or more consecutive resource blocks on afrequency axis.

Effects of the Invention

According to the present invention, system throughput can be improved byholding down an increase of the overhead due to scheduling informationwhile enhancing the multi-user diversity effect. This is because thepresent invention is configured to set an appropriate frequency blockcount depending upon the environment or condition of communications inthe base station (cell) or mobile station.

Thus, the overhead due to scheduling information averaged for the wholecell can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A diagram showing a mobile communications system in a firstembodiment.

FIG. 2 A block diagram showing a main configuration of a base station inthe mobile communications system to which the first embodiment isapplied.

FIG. 3 A block diagram showing a main configuration of a mobile stationin the mobile communications system to which the first embodiment isapplied.

FIG. 4 A chart showing an operation flow of the base station and mobilestation in the first embodiment.

FIG. 5 A schematic table showing a first example of selection of amaximum frequency block count in accordance with the first embodiment.

FIG. 6 A schematic table showing a second example of selection of amaximum frequency block count in accordance with the first embodiment.

FIG. 7 A diagram showing a mobile communications system in a secondembodiment.

FIG. 8 A block diagram showing a main configuration of a base station ina mobile communications system to which the second embodiment isapplied.

FIG. 9 A chart showing an operation flow of the base station and mobilestation in the second embodiment.

FIG. 10 A schematic table showing a first example of selection of amaximum frequency block count in accordance with the second embodiment.

FIG. 11 A schematic table showing a second example of selection of amaximum frequency block count in accordance with the second embodiment.

FIG. 12 A block diagram showing a main configuration of a base stationin a mobile communications system to which a third embodiment isapplied.

FIG. 13 A block diagram showing a main configuration of a mobile stationin the mobile communications system to which the third embodiment isapplied.

FIG. 14 A chart showing an operation flow of the base station and mobilestation in the third embodiment.

FIG. 15 A block diagram showing a main configuration of a base stationin a mobile communications system to which a fourth embodiment isapplied.

FIG. 16 A chart showing an operation flow of the base station and mobilestation in the fourth embodiment.

FIG. 17 A diagram showing an example of resource block allocation in anLTE downlink.

FIG. 18 A diagram showing an example of resource block allocation in anLTE uplink.

FIG. 19 A diagram showing SC-FDMA and MC-FDMA transmitterconfigurations, and their spectra.

FIG. 20 A diagram for explaining a method of adding a cyclic prefix.

FIG. 21 A system diagram for explaining a system for a techniquerelating to the present invention.

FIG. 22 A diagram for explaining a CAZAC sequence for use in a referencesignal in the present invention.

FIG. 23 An operation flow chart for a base station and a mobile stationin downlink control in the second embodiment.

FIG. 24 An operation flow chart for a base station and a mobile stationin downlink control in the third embodiment.

EXPLANATION OF SYMBOLS

20, 80, 120 Base station

30, 130 Mobile station

BEST MODES FOR CARRYING OUT THE INVENTION

The present invention is characterized in setting a frequency blockcount to be allocated to the same user to an appropriate value based ona communication capability, a communication environment, and systeminformation, which is information affecting the communicationenvironment, for a base station or a mobile station. That is, it ischaracterized in setting a maximum frequency block count, which is thelargest value of the frequency block count to be allocated to the sameuser, to an appropriate value. By imposing a limit on the frequencyblock count, an increase of the overhead due to scheduling informationaveraged for the whole cell is prevented. It should be noted that thefrequency block refers to a resource block group comprised of one ormore consecutive resource blocks.

In MC-FDMA, in which an output of transmitter DFT (Discrete FourierTransform) in DFT-spread-OFDM (Discrete FourierTransform-spread-Orthogonal Frequency Division Multiplexing) isallocated to at least one or more resource block groups described above,an increase of PAPR in mobile stations in the periphery of a cell isproblematic unless a limit is imposed on the frequency block countbecause PAPR is increased as the frequency block count becomes higher.According to the present invention, the problem of the PAPR increase inmobile stations in the periphery of a cell is avoided by setting anmaximum allowable frequency block count on a base station (cell)-by-basestation basis, on a mobile station-by-mobile station basis, or on amobile station group-by-mobile station group basis, based on informationsuch as system information for a base station or a mobile station.

In particular, in circumstances where it is desirable to enhance themulti-user diversity effect (where the system band is wide, where CQI isacceptable, or the like), the maximum frequency block count is set to alarger value; in circumstances where it is desirable to hold down anincrease of the overhead (where the system band is narrow, where CQI ispoor, or the like), the maximum frequency block count is set to asmaller value.

Subsequently, a technique relating to resource block allocation inaccordance with the present invention will be described with referenceto the accompanying drawings.

First Embodiment

In a first embodiment, a configuration in which the maximum frequencyblock count is selected on a base station (cell)-by-base station basiswill be described.

FIG. 1 is a diagram showing a case in which the maximum frequency blockcount is switched according to the size of a base station (cell).

In this case, since a sufficient margin of the transmit power may beallowed for a smaller cell size, the transmit bandwidth can beincreased. In such a case, since a greater multi-diversity effect can beexpected, the frequency block count is set to a larger value. On theother hand, since a base station (cell) with a larger cell size allowsfor an insufficient margin of the transmit power, the transmit bandwidthis reduced. In such a case, since a greater multi-diversity effectcannot be expected, the maximum frequency block count is decreased toreduce the overhead due to scheduling information.

FIG. 2 is a block diagram showing a main configuration of a base stationin a mobile communications system to which the first embodiment isapplied. It is assumed here that a base station 20 accommodates aplurality of mobile stations 30 (UE1, UE2, . . . ). The base station andmobile stations communicate with one another using an OFDM (OrthogonalFrequency Division Multiplexing) scheme or an MC-FDMA scheme.

A wireless communication control section 201 controls communicationswith the plurality of mobile stations UE. For example, the wirelesscommunication control section 201 separates multiplexed signals receivedfrom the plurality of mobile stations UE and outputs them to an uplinkdata reproducing section 202, an uplink control signal reproducingsection 203 and an uplink CQI measuring section 204; it also multiplexesseveral kinds of transmit signals from a downlink data generatingsection 208, a downlink control signal generating section 209 and adownlink reference signal generating section 210 according to afrequency/time multiplexing configuration determined at a scheduler 207,and transmits them to the plurality of mobile stations.

The uplink CQI measuring section 204 receives sounding reference signalsfrom the mobile stations UE to measure an uplink CQI, and outputs it tothe control section 205 and scheduler 207. As used herein, a soundingreference signal is a reference signal for use in uplink CQI measurementor link adaptation, and is transmitted by a mobile station to a basestation (the signal being sometimes referred to as pilot signal).

A maximum frequency block count determining section 206 accepts systeminformation as input from the control section 205, which informationindicates the cell size for the own base station, and the communicationcapability of the base station such as the system bandwidth of the cell.The maximum frequency block count determining section 206 looks up adetermination criterion storage 211 to determine a maximum frequencyblock count specific to the cell according to the supplied systeminformation, and outputs it to the control section 205. It should benoted that a determination criterion table stored in the determinationcriterion storage 211 may be factory-supplied, or may be appropriatelyset or modified during installation or after installation in the field.

The scheduler 207 uses the uplink CQI measured for each mobile stationUE while taking account of the maximum frequency block count determinedat the maximum frequency block count determining section 206 to makechannel-dependent frequency scheduling (resource allocation) undercontrol of the control section 205. The scheduler 207 outputs a resultof downlink data scheduling to the downlink data generating section anda-result of uplink data scheduling (scheduling information) to thedownlink control generating section 209, which are in turn transmittedto the mobile stations by the wireless communication control section201. Now the transmission of a result of scheduling transmitted tomobile stations will be described below. A resource allocation field inscheduling information (UL grant) notified through a downlink controlsignal is composed of one or more resource indication values (RIV). Aresource indication value RIV_(n) for an n-th frequency block representsa start resource block (RB_(start,n)) or start position, and a length(L_(CRBs,n)) or the number of consecutive resource blocks. The resourceindication value RIV_(n) is notified to a mobile station with PhysicalDownlink Control Channel (PDCCH), for example. N_(RIV) represents themaximum number of resource indication values, that is, the maximumfrequency block count, where the value of N_(RIV) is broadcast as partof system information. An n-th resource indication value RIV_(n) isdefined by EQ. 1 below. It should be noted that L_(CRBs,n) andRB_(start,n) may be broadcast as separate pieces of information.

if

(L _(CRBs,n)−1)≤└N _(RB) ^(UL)/2┘

then

RIV_(n) =N _(RB) ^(UL)(L _(CRBs,n)−1)+RB_(START,n)

else

RIV_(n) =N _(RB) ^(UL)(N _(RB) ^(UL) −L _(CRBs,n)+1)+(N _(RB)^(UL)−1−RB_(START,n))   (EQ. 1)

where N^(UL) _(RB) is the number of resource blocks in the whole system.

Moreover, N_(RIV) is sent through a higher layer control signal mappedto Physical Broadcast Channel (PBCH) or Physical Downlink Shared Channel(PDSCH). It should be noted that the initial value of N_(RIV) is definedas a fixed value beforehand, or sent through a higher layer controlsignal mapped to PBCH or PDSCH.

FIG. 3 is a block diagram showing a main configuration of a mobilestation in the mobile communications system to which the firstembodiment is applied. Since the mobile station 30 does not performresource management, resource blocks for use in transmission/receptionis set according to a downlink control signal received from the basestation 20.

In FIG. 2, from multiplexed signals received from the base station 20 bya wireless communication control section 301, a downlink referencesignal is used to make CQI measurement at the CQI measuring section 302,and scheduling information is extracted by the downlink control signalreproducing section 303. According to the scheduling informationnotified by the base station, the control section 304 controls an uplinkdata generating section 305, an uplink reference signal generatingsection 306, an uplink control signal generating section 307, and asub-carrier mapping section 308 in the wireless communication controlsection 301.

According to the scheduling information notified by the base station viathe downlink control signal, the sub-carrier mapping section 308performs subcarrier mapping, and data is transmitted.

Especially in a case that a frequency block count of one or more is usedto perform data transmission in MC-FDMA, a CAZAC (Constant AmplitudeZero Auto-Correlation) sequence used in a reference signal (sometimesreferred to as demodulation reference signal) for use in demodulation ofPUSCH (Physical Uplink Shared Channel; through which user data is mainlytransmitted) has a sequence length matching the transmit bandwidth ofall frequency blocks, not the bandwidth of each frequency block.

As one example, assume that transmission is made with sub-carriermapping as shown in FIG. 22 in a condition that the number ofsub-carriers is 200, the frequency block count is two, and the number ofIFFT points is 512. In this case, a CAZAC sequence matching the transmitbandwidth of all frequency blocks, which is the transmit bandwidth ofthe two frequency blocks in this example because the transmit bandwidthof each frequency block is 100 (reference symbols 22B and 22E in FIG.22), is caused, and then, is transformed into signals in the frequencydomain at the DFT section, and sub-carrier mapping is applied to thesame band as that for transmitting PUSCH (data signal) for spreading. Atthat time, the band through which no PUSCH is transmitted (22A, 22C,22D, and 22F in FIG. 22) is filled with zero.

It should be noted that the CAZAC sequence refers to a sequence having aconstant amplitude and an autocorrelation value of zero at a non-zerophase difference both in the time and frequency domains. Since PAPR canbe held down to a smaller value because of a constant amplitude in thetime domain, and since the amplitude is also constant in the frequencydomain, it is a sequence suitable for channel estimation in thefrequency domain. The sequence also has an advantage that it is suitablefor timing detection for received signals because of its perfectautocorrelation property.

FIG. 4 shows an operation flow of the base station and mobile station inthe first embodiment. In FIG. 4, steps indicated by solid-line boxesdesignate an operation of the base station, and those indicated bydotted-line boxes designate an operation of the mobile station.

First, the control section 205 in the base station inputs systeminformation such as the cell size for the own base station to themaximum frequency block determining section 206 (Step 401).

Next, the maximum frequency block determining section 206 looks up thedetermination criterion storage 211, and selects a maximum frequencyblock count specific to the base station depending upon the systeminformation (Step 402).

Next, the CQI measuring section 302 in the mobile station UE uses adownlink reference signal to measure downlink CQI (Step 403).

An uplink control signal written with the downlink CQI measured at Step403 is generated at the uplink control signal generating section 307,and is transmitted via the wireless communication control section 301 tothereby notify the downlink CQI to the base station (Step 404).

The control section 205 in the base station determines a band for anuplink sounding reference signal based on the downlink CQI notified atStep 404 (Step 405), and notifies it to the mobile station via thedownlink control signal (Step 406).

The uplink reference signal generating section 306 in the mobile stationtransmits a sounding reference signal according to the notification atStep 406 (Step 407).

The uplink CQI measuring section 204 in the base station receives thesounding reference signal transmitted at Step 407, and measures CQI(Step 408).

Next, the scheduler 207 in the base station makes scheduling so that thefrequency block count is equal to or smaller than the maximum frequencyblock count selected by the maximum frequency block count determiningsection 206 at Step 402 (Step 409), and notifies the schedulinginformation to the mobile station through a downlink control signal(Step 410). At that time, the downlink control signal generating section209 generates a resource indication value RIV_(n) using EQ. (1) givenearlier, and notifies it.

Finally, the wireless communication control section 301 in the mobilestation transmits uplink data according to the notification at Step 410(Step 411). At that time, it causes a CAZAC sequence matching thetransmit bandwidth of all frequency blocks, transforms the sequence intosignals in the frequency domain at the DFT section, and then,sub-carrier maps a reference signal for use in demodulation of data inthe same band as that for transmitting data signals. The data signal andreference signal are time division multiplexed (TDM).

In the first embodiment, the maximum frequency block count (N_(RIV))selected at Step 402 may be notified by the base station to the mobilestation through a higher layer control signal mapped to PhysicalBroadcast Channel (PBCH) or Physical Downlink Shared Channel (PDSCH). Itis believed that uplink scheduling information (UL grant) contained inthe downlink control signal becomes larger for a higher frequency blockcount. In this case, the base station may notify the maximum frequencyblock count to the mobile station, and determine a range of detection ofa downlink control signal based on the maximum frequency block count,whereby a range of the scheduling information looked up by the mobilestation can be confined. As a result, processing of detecting a controlsignal can be reduced.

Now a first example of setting of a maximum frequency block countaccording to the first embodiment of the present invention will bedescribed. In this example, a maximum frequency block count isdetermined depending upon the cell size, which is information affectingthe communication environment. FIG. 5 is an example of a table stored inthe aforementioned determination criterion storage 211. The cell sizeshown is larger for a larger value (3>2>1). In particular, for cell 1and cell 2 having a smaller cell size of one, the maximum frequencyblock count is set to four; for cell 3 having a cell size of two, themaximum frequency block count is set to two; and for cell 4 having alarger cell size of three, the maximum frequency block count is set toone, with which the problem of PAPR is smaller.

A second example of selection of a maximum frequency block countaccording to the first embodiment of the present invention will bedescribed. In this example, a maximum frequency block count isdetermined depending upon the system bandwidth in the base station(cell), which is information about the communication environment. FIG. 6is an example of a table stored in the aforementioned determinationcriterion storage 211. In particular, cell 1 and cell 3 have a largersystem bandwidth of 50 MHz. Thus, the maximum frequency block count isset to four to aim at the multi-user diversity effect. Cell 2 has asmaller system bandwidth of 1.25 MHz. Therefore, a large multi-userdiversity effect cannot be expected, so that the maximum frequency blockcount is set to one to reduce the overhead due to schedulinginformation. Since cell 4 has a system bandwidth of 20 MHz, the maximumfrequency block count is set to two, taking account of a tradeoffbetween the multi-user diversity effect and the overhead.

It should be noted that information for use in selection of a maximumfrequency block count may be information other than the cell size orsystem bandwidth described above. For example, it may be informationabout the communication environment such as the coverage of a basestation, channel quality information measured by a downlink referencesignal, bandwidth of downlink data signals, and number of levels inmulti-level modulation for downlink data signals, or informationaffecting the communication environment such as the code rate. Moreover,since the cell size described above is determined by informationaffecting the communication environment such as the position of a basestation, distance between base stations, and interference power, themaximum frequency block count may be selected using such information.

According to the first embodiment, an appropriate maximum frequencyblock count is set on a base station (cell)-by-base station basisdepending upon system information such as the cell size or systembandwidth, so that improvement of throughput can be expected independentof an access scheme (OFDM, MC-FDMA, etc.). Moreover, an effect ofsimplifying processing at a mobile station can be expected bybroadcasting the amount of information on scheduling, which varies withthe maximum frequency block count.

Furthermore, when switching the maximum frequency block count accordingto, for example, the cell size, an increase of PAPR can be prevented byreducing the frequency block count in MC-FDMA, and therefore, anadditional effect can be expected. In particular, PAPR in mobilestations in the periphery of a cell is problematic for a cell having alarger size, and accordingly, the maximum frequency block count isreduced to avoid an increase of PAPR. On the other hand, a cell that hasa smaller size and is isolated with smaller interference effects fromother cells has a sufficient margin of the transmit power and PAPR isnot significantly problematic, so that the maximum frequency block countis set to a larger value to aim at improvement of throughput from themulti-diversity effect.

Further, in a case that a frequency block count of one or more is usedto perform transmission in MC-FDMA, the property of a CAZAC sequence foruse in a reference signal for use in demodulation of PUSCH is preventedfrom being deteriorated even in transmission using a plurality offrequency blocks by matching the CAZAC sequence for the reference signalto a transmit bandwidth of all frequency blocks. Thus, a PAPR propertyand channel quality measurement precision equivalent to those forfrequency block count=1 can be obtained.

It should be noted that setting of a maximum frequency block count maybe performed at initial setting in installation of a base station, eachtime scheduling is made, periodically, or at discretion.

Second Embodiment

While the maximum frequency block count is selected on a base station(cell)-by base station basis in the first embodiment, it is selected ona mobile station UE-by-mobile station basis in a second embodiment.

For example, a maximum frequency block count is determined according toa mobile station class (sometimes referred to as UE class) for eachmobile station. The mobile station class refers to a class of thecapability of a mobile station classified according to information onthe communication capability of the mobile station, such as the transmitbandwidth, peak rate of transmission data, and number of transmitantennas, where a higher mobile station class corresponds to a mobilestation capable of transmission at a higher speed. In particular, amobile station of a low mobile station class has a smaller transmittablebandwidth. In this case, since the multi-user diversity effect, which isobtained by a multiplicity of discrete resource blocks (frequencyblocks) allocated on a frequency axis, becomes smaller, the maximumfrequency block count is reduced to aim at reduction of the overhead. Onthe other hand, a mobile station of a higher mobile station class has alarger transmittable bandwidth. In this case, since the multi-userdiversity effect, which is obtained by discrete resource blocksallocated on a frequency axis, is enhanced, the maximum frequency blockcount is increased to aim at improvement of throughput.

Moreover, when the access scheme is MC-FDMA, a maximum frequency blockcount may be selected depending upon CQI of each mobile station. FIG.7(a) is a system diagram in selecting a maximum frequency block countaccording to CQI of a mobile station. For mobile stations in theperiphery of a cell, the maximum frequency block count is set to one toavoid an increase of PAPR, and coverage is enlarged. On the other hand,since PAPR is not significantly problematic in other mobile stations,the maximum frequency block count is set to a larger value, such as two,four, to aim at improvement of throughput from the multi-diversityeffect. FIG. 7(b) is a diagram showing a relationship between a CQIlevel and a maximum frequency block count, where the maximum frequencyblock count is set to a larger value for a higher CQI level.

FIG. 8 is a block diagram showing a main configuration of a base stationin a mobile communications system to which the second embodiment isapplied. Since this is generally similar to that in the firstembodiment, differences will be described below.

In the second embodiment, CQI measured at the uplink CQI measuringsection 204 is input to the maximum frequency block count determiningsection 206. The maximum frequency block count determining section 206looks up the determination criterion storage 211 to determine a maximumfrequency block count specific to the mobile station, and outputs it tothe control section 205. It should be noted that a determinationcriterion table stored in the determination criterion storage 211 may befactory-supplied, or may be appropriately set or modified duringinstallation or after installation in the field.

The maximum frequency block count determining section 206 determines amaximum frequency block count based on the CQI measured at the uplinkCQI measuring section 204 and on information supplied by the controlsection 205 and contained in an uplink control signal from the mobilestation UE (mobile station class, type of data transmission, etc.), andoutputs it to the control section 205. It should be noted that indetermining the maximum frequency block count, time-averaged CQImeasured for reducing an effect such as an interference effect fromother cells may be employed.

The main configuration of the mobile station UE in the mobilecommunications system to which the second embodiment is applied issimilar to that of the first embodiment shown in FIG. 3, and therefore,explanation thereof will be omitted.

FIG. 9 shows an operation flow of the base station and mobile station inthe second embodiment. In FIG. 9, steps indicated by solid-line boxesdesignate an operation of the base station, and those indicated bydotted-line boxes designate an operation of the mobile station.

First, the CQI measuring section 302 in the mobile station UE uses adownlink reference signal to measure downlink CQI (Step 901).

An uplink control signal written with the downlink CQI measured at Step901 is generated at the uplink control signal generating section 307,and is transmitted via the wireless communication control section 301 tothereby notify the downlink CQI to the base station (Step 902).

The scheduler 207 in the base station determines a band for an uplinksounding reference signal based on the downlink CQI notified at Step 902(Step 903), and the downlink control signal generating section 209generates a downlink control signal written with it, which istransmitted via the wireless communication control section 301 to benotified to the mobile station UE (Step 904).

The uplink reference signal generating section 306 in the mobile stationUE generates a sounding reference signal according to the notificationat Step 904, and transmits it (Step 905).

The uplink CQI measuring section 204 in the base station receives thesounding reference signal transmitted at Step 905 to make uplink CQImeasurement (Step 906).

The uplink CQI measuring section 204 in the base station inputs theuplink CQI measured at Step 906 to the maximum frequency blockdetermining section 206 (Step 907).

The maximum frequency block determining section 206 looks up thedetermination criterion storage 211 to determine a maximum frequencyblock count according to the uplink CQI (Step 908).

Next, the scheduler 207 in the base station makes scheduling so that thefrequency block count is equal to or smaller than the maximum frequencyblock count determined at Step 908 (Step 909), and notifies thescheduling information to the mobile station through a downlink controlsignal (Step 910). At that time, the downlink control signal generatingsection 209 defines a resource indication value RIV_(n) using EQ. (1)given earlier, and notifies it.

Finally, the wireless communication control section 301 in the mobilestation transmits uplink data according to the notification at Step 910(Step 911). At that time, it causes a CAZAC sequence matching thetransmit bandwidth of all frequency blocks, transforms the sequence intosignals in the frequency domain at the DFT section, and then,sub-carrier maps a reference signal in the same band as that fortransmitting data signals. The data signal and reference signal are timedivision multiplexed (TDM).

Moreover, the base station may notify the maximum frequency block count(N_(RIV)) determined at Step 908 to the mobile station at Step 910through a higher layer control signal mapped to PDSCH. It is believedthat uplink scheduling information (UL grant) contained in the downlinkcontrol signal becomes larger for a higher frequency block count. Inthis case, the base station may notify the maximum frequency block countto the mobile station, and determine a range of detection of a downlinkcontrol signal based on the maximum frequency block count, whereby arange of the scheduling information looked up by the mobile station canbe confined. As a result, processing of detecting a control signal canbe reduced.

Now a first example of selection of a maximum frequency block countaccording to the second embodiment of the present invention will bedescribed. In this example, a maximum frequency block count is set basedon uplink CQI measured using an uplink sounding reference signal, whichis information about the communication environment. FIG. 10 is anexample of a table stored in the aforementioned determination criterionstorage 211. The CQI level shown represents a larger size for a largervalue (31>30, . . . , 1>0; when five bits are used in the current case,there are 32 levels). In this example, the maximum frequency block countis switched according to the measured CQI level. In particular, sincethe CQI level for UE1 is as high as 27, the maximum frequency blockcount is set to four; since the CQI levels for UE2 and UE4 are 18, 12,respectively, the maximum frequency block count is set to two; and sinceUE3 has a CQI level as low as three, the maximum frequency block countis set to one for eliminating the problem of PAPR.

A second example of selection of a maximum frequency block countaccording to the second embodiment of the present invention will bedescribed. While the maximum frequency block count is determineddepending upon the measured uplink CQI in the example above, the examplehere addresses a case in which the maximum frequency block count is setaccording to the mobile station class written in control information.The mobile station class refers to a communication capability of amobile station defined by a condition of a mobile station, such as thetransmit bandwidth, peak rate of transmission data, or number oftransmit antennas. FIG. 11 shows an example of a table stored in theaforementioned determination criterion storage 211. The mobile stationclass is higher for a larger value. In particular, since UE1 has amobile station class as high as three, the transmittable bandwidth islarge. Thus, the maximum frequency block count is set to four to aim atthe multi-user diversity effect. Since UE2 and UE4 have a mobile stationclass of one; the transmittable bandwidth is smaller. Thus, a largemulti-user diversity effect cannot be expected, so that the maximumfrequency block count is set to one to reduce the overhead due toscheduling information. Since UE3 has a mobile station class of two, themaximum frequency block count is set to two, taking account of atradeoff between the multi-user diversity effect and the overhead.

While a case in which the maximum number of groups is determined basedon the mobile station class and CQI measured by a sounding referencesignal is addressed here, it may be contemplated that the secondembodiment uses information about a communication environment, such asthe bandwidth of an uplink sounding reference signal, bandwidth used inuplink data transmission, number of levels in multi-level modulation andcode rate used in uplink data transmission, transmittable/receivablebandwidth of a mobile station (sometimes referred to as UE capability),and type of uplink transmission data (VoIP, HTTP, FTP etc.), orinformation affecting the communication environment, such as the billingscheme in which a user signs on, power headroom (which is a differencebetween the maximum transmit power of a mobile station and an actualtransmit power of the mobile station), and target SINR in uplink powercontrol.

Moreover, while the description has been made on a case in which themaximum frequency resource block count is determined on a mobilestation-by-mobile station basis, mobile stations may be divided intogroups based on a certain condition and the maximum frequency resourceblock count may be determined on a group-by-group basis.

Moreover, while allocation of uplink resource blocks is mainlydescribed, the present invention is not limited thereto, and it isapplicable to allocation of downlink resource blocks. An operation inthis case will now be described with reference to FIG. 23.

First, the CQI measuring section 302 in the mobile station UE uses adownlink reference signal to measure downlink CQI (Step 2301).

An uplink control signal written with the downlink CQI measured at Step901 is generated at the uplink control signal generating section 307,and is transmitted via the wireless communication control section 301 tothereby notify the downlink CQI to the base station (Step 2302).

The control section 205 in the base station inputs the downlink CQInotified at Step 2302 to the maximum frequency block count determiningsection 206 (Step 2303).

The maximum frequency block determining section 206 looks up thedetermination criterion storage 211 to determine a maximum frequencyblock count according to the downlink CQI (Step 2304).

Next; the scheduler 207 in the base station makes scheduling so that thefrequency block count is equal to or smaller than the maximum frequencyblock count determined at Step 2304 (Step 2305).

Finally, the wireless communication control section 201 transmitsdownlink data based on a result of scheduling at Step 2305 (Step 2306).At that time, it causes a CAZAC sequence matching the transmit bandwidthof all frequency blocks, transforms the sequence into signals in thefrequency domain at the DFT section, and then, sub-carrier maps areference signal in the same band as that for transmitting data signals.The data signal and reference signal are time division multiplexed(TDM).

According to the second embodiment, an appropriate maximum frequencyblock count is set on a mobile station-by-mobile station basis dependingupon the environment or condition of communications in the base stationor mobile station, whereby further improvement of throughput can beexpected independent of an access scheme (OFDM, MC-FDMA, etc.).Moreover, an effect of simplifying processing at the mobile station canbe expected by notifying the amount of information on scheduling, whichvaries with the maximum frequency block count, from the base station tothe mobile station.

Furthermore, when switching the maximum frequency block count accordingto, for example, the CQI, an increase of PAPR can be prevented byreducing the frequency block count in MC-FDMA, and therefore, anadditional effect can be expected. In particular, PAPR is problematic inmobile stations having poor CQI, and accordingly, the maximum frequencyblock count is reduced to avoid an increase of PAPR. On the other hand,in mobile stations in which CQI is acceptable and PAPR is notsignificantly problematic, the maximum frequency block count may be setto a larger value to aim at improvement of throughput from themulti-diversity effect.

Further, in a case that a frequency block count of one or more is usedto perform transmission in MC-FDMA, the property of a CAZAC sequence foruse in a reference signal for use in demodulation of PUSCH is preventedfrom being deteriorated even in transmission using a plurality offrequency blocks by matching the CAZAC sequence for the reference signalto a transmit bandwidth of all frequency blocks. Thus, a PAPR propertyand channel quality measurement precision equivalent to those forfrequency block count=1 can be obtained.

Third Embodiment

In the first and second embodiments, the maximum frequency block countis determined by a base station. According to a third embodimentdescribed below, the maximum frequency block count is determined by amobile station.

A system diagram in a mobile communications system to which the thirdembodiment is applied is similar to that of the second embodiment shownin FIG. 7, and therefore, explanation thereof will be omitted. Since themobile station determines the maximum frequency block count in the thirdembodiment, the maximum frequency block count basically has a valuespecific to the mobile station.

FIGS. 12, 13 are block diagrams showing the main configurations of abase station and a mobile station in a mobile communications system towhich the second embodiment is applied. Since in the third embodiment,the maximum frequency block count is determined by a mobile station, themaximum frequency block count determining section 206 and determinationcriterion storage 211 in FIG. 2 are configured within a mobile stationin FIG. 13 (a maximum frequency block count determining section 1301 anda determination criterion storage 1302). The CQI measuring section 302inputs the CQI to the maximum frequency block count determining section1301. The maximum frequency block count determining section 1301 looksup the determination criterion storage 1302 to determine a maximumfrequency block count specific to the mobile station, and outputs it tothe control section 304. It should be noted that a determinationcriterion table stored in the determination criterion storage 1302 maybe factory-supplied, or may be appropriately set at the start ofoperation or modified during operation.

Description of other portions will be omitted because they are similarto those described regarding the first and second embodiments.

FIG. 14 shows an operation flow of the base station and mobile stationin the third embodiment. In FIG. 14, steps indicated by solid-line boxesdesignate an operation of the base station, and those indicated bydotted-line boxes designate an operation of the mobile station.

First, the CQI measuring section 302 in the mobile station measuresdownlink CQI using a downlink reference signal (Step 1401).

Next, the CQI measuring section 302 inputs the downlink CQI measured atStep 1401 to the maximum frequency block count determining section 1301(Step 1402).

Next, the maximum frequency block count determining section 1301 looksup the determination criterion storage 1302 to determine a maximumfrequency block count according to the downlink CQI (Step 1403).

Next, the CQI measured by the CQI measuring section 302 at Step 1401 andmaximum frequency block count determined at Step 1403 are notified tothe base station through an uplink control signal (Step 1404).

The scheduler 207 in the base station determines a band for an uplinksounding reference signal based on the downlink CQI notified at Step1404 (Step 1405), and notifies it to the mobile station via the downlinkcontrol signal (Step 1406).

The uplink reference signal generating section 306 in the mobile stationtransmits a sounding reference signal according to the notification atStep 1406 (Step 1407).

The uplink CQI measuring section 204 in the base station receives thesounding reference signal transmitted at Step 1407 and makes CQImeasurement (Step 1408).

Next, the scheduler 207 in the base station makes scheduling so that thefrequency block count is equal to or smaller than the maximum frequencyblock count selected at Step 1403 (Step 1409), and notifies thescheduling information to the mobile station through a downlink controlsignal (Step 1410). At that time, the downlink control signal generatingsection 209 generates a resource indication value RIV_(n) using EQ. (1)given earlier, and notifies it.

Finally, the wireless communication control section 301 in the mobilestation transmits uplink data according to the notification at Step 1410(Step 1411). At that time, it causes a CAZAC sequence matching thetransmit bandwidth of all frequency blocks, transforms the sequence intosignals in the frequency domain at the DFT section, then, sub-carriermaps a reference signal in the same band as that for transmitting datasignals, and transmits the signals. The data signal and reference signalare time division multiplexed (TDM).

While a case in which the maximum frequency block count is determinedbased on the CQI measured using a downlink reference signal is addressedhere, it may be contemplated to use information affecting thecommunication environment, such as the power headroom, and remainingpower of a battery in the mobile station, or information about acommunication environment, such as the transmittable/receivablebandwidth of a mobile station (sometimes referred to as UE capability),mobile station class, and type of uplink transmission data (VoIP, HTTP,FTP etc.).

According to the third embodiment, the mobile station can take theinitiative to determine the maximum frequency block count. Moreover,since the mobile station determines the maximum frequency block count,the base station need not notify the maximum frequency block count tothe mobile station, and an effect of simplifying processing at themobile station described regarding the first and second embodiments canbe expected.

Moreover, the present invention is not limited to application to anyspecific access scheme such as OFDM or MC-FDMA.

Moreover, while the description has been mainly made on an uplink, thepresent invention is not limited thereto, and is applicable to adownlink. An operation in this case will now be described with referenceto FIG. 24.

First, the CQI measuring section 302 in the mobile station UE uses adownlink reference signal to measure downlink CQI (Step 2401).

Next, the maximum frequency block count determining section 1301 looksup the determination criterion storage 1302 to determine a maximumfrequency block count according to the downlink CQI (Step 2402).

Next, the CQI measured by the CQI measuring section 302 at Step 1401 andthe maximum frequency block count determined at Step 1403 are notifiedto the base station through an uplink control signal (Step 2403).

Next, the scheduler 207 in the base station makes scheduling so that thefrequency block count is equal to or smaller than the maximum frequencyblock count determined at Step 2403 (Step 2404).

Finally, the wireless communication control section 201 transmitsdownlink data based on a result of scheduling at Step 2305 (Step 2405).At that time, it causes a CAZAC sequence matching the transmit bandwidthof all frequency blocks, transforms the sequence into signals in thefrequency domain at the DFT section, and then, sub-carrier maps areference signal in the same band as that for transmitting data signals.The data signal and reference signal are time division multiplexed(TDM).

According to the third embodiment, an appropriate maximum frequencyblock count is set on a mobile station-by-mobile station basis, wherebyfurther improvement of throughput can be expected independent of anaccess scheme (OFDM, MC-FDMA, etc.).

Moreover, when switching the maximum frequency block count according to,for example, the CQI, an increase of PAPR can be prevented by reducingthe frequency block count in MC-FDMA, and therefore, an additionaleffect can be expected, In particular, PAPR is problematic in mobilestations having poor CQI, and accordingly, the maximum frequency blockcount is reduced to avoid an increase of PAPR. On the other hand, inmobile stations in which CQI is acceptable and PAPR is not significantlyproblematic, the maximum frequency block count may be set to a largervalue to aim at improvement of throughput from the multi-diversityeffect.

Furthermore, in a case that a frequency block count of one or more isused to perform transmission in MC-FDMA, the property of a CAZACsequence for use in a reference signal for use in demodulation of PUSCHis prevented from being deteriorated even in transmission using aplurality of frequency blocks by matching the CAZAC sequence for thereference signal to a transmit bandwidth of all frequency blocks. Thus,a PAPR property and channel quality measurement precision equivalent tothose for frequency block count=1 can be obtained.

While the description has been made on a case in which the maximumfrequency resource block count is determined on a mobilestation-by-mobile station basis, mobile stations may be divided intogroups based on a certain condition and the maximum frequency resourceblock count may be determined based on a group to which the own mobilestation belongs.

Fourth Embodiment

In the second embodiment described above, the maximum frequency blockcount is determined by the mobile station based on uplink CQI. Accordingto a fourth embodiment described below, the maximum frequency blockcount is determined by the base station based on downlink CQI, which isinformation about a communication environment.

FIG. 15 is a block diagram showing a main configuration of a basestation in a mobile communications system to which the fourth embodimentis applied. Since the configuration is generally similar to that in thesecond embodiment, differences will be described below.

In the fourth embodiment, the maximum frequency block count isdetermined by a base station based on downlink CQI, so that the uplinkcontrol signal reproducing section inputs the downlink CQI contained inan uplink control signal to the maximum frequency block countdetermining section. The maximum frequency block count determiningsection looks up the determination criterion storage to determine amaximum frequency block count specific to the mobile station, andoutputs it to the control section. It should be noted that thedetermination criterion table stored in the determination criterionstorage 211 may be factory-supplied, or may be appropriately set at thestart of operation or modified during operation.

Since the main configuration of the mobile station UE in the mobilecommunications system to which the fourth embodiment is applied issimilar to that of the first and second embodiments shown in FIG. 3,explanation thereof will be omitted.

FIG. 16 shows an operation flow of the base station and mobile stationin the fourth embodiment. In FIG. 16, steps indicated by solid-lineboxes designate an operation of the base station, and those indicated bydotted-line boxes designate an operation of the mobile station.

First, the CQI measuring section 302 in the mobile station uses adownlink reference signal to measure downlink CQI (Step 1).

Next, an uplink control signal written with the downlink CQI measured atStep 1 is generated at the uplink control signal generating section 307,and is transmitted via the wireless communication control section 301 tothereby notify the downlink CQI to the base station (Step 2). Next, thecontrol section 205 in the base station inputs the downlink CQI to themaximum frequency block count determining section 206 (Step 3). Next,the maximum frequency block count determining section 206 looks up thedetermination criterion storage 211 to determine a maximum frequencyblock count according to the downlink CQI (Step 4).

The scheduler 207 in the base station determines a band for an uplinksounding reference signal based on the downlink CQI notified at Step 4(Step 5), and the downlink control signal generating section 209generates a downlink control signal written with the band, transmits thegenerated downlink control signal via the wireless communication controlsection 301, and thereby notifies it to the mobile station (Step 6).

The mobile station uplink reference signal generating section 306generates a sounding reference signal according to the notification atStep 6, and transmits it (Step 7).

The uplink CQI measuring section 204 in the base station receives thesounding reference signal transmitted at Step 7, and makes uplink CQImeasurement (Step 8).

Next, the uplink CQI measuring section 204 in the base station inputsthe uplink CQI measured at Step 8 to the maximum frequency blockdetermining section 206, makes scheduling using the measured uplink CQIso that the frequency block count is equal to or smaller than themaximum frequency block count selected at Step 4 (Step 9), and notifiesthe scheduling information to the mobile station via the downlinkcontrol signal (Step 10). At that time, the downlink control signalgenerating section 209 generates a resource indication value RIV_(n)using EQ. (1) given earlier, and notifies it.

Finally, the wireless communication control section 301 in the mobilestation transmits uplink data according to the notification at Step 10(Step 11). At that time, it causes a CAZAC sequence matching thetransmit bandwidth of all frequency blocks, transforms the sequence intosignals in the frequency domain at the DFT section, then, sub-carriermaps a reference signal in the same band as that for transmitting datasignals, and transmits the signals. The data signal and reference signalare time division multiplexed (TDM).

Moreover, the maximum frequency block count (N_(RIV)) determined at Step908 may be notified by the base station to the mobile station at Step910 through a higher layer control signal mapped to PDSCII. It isbelieved that uplink scheduling information (UL grant) contained in thedownlink control signal becomes larger for a higher frequency blockcount. In this case, the base station may notify the maximum frequencyblock count to the mobile station, and determine a range of detection ofa downlink control signal based on the maximum frequency block count,whereby a range of the scheduling information looked up by the mobilestation can be confined. As a result, processing of detecting a controlsignal can be reduced.

According to the fourth embodiment, an appropriate maximum frequencyblock count is set on a mobile station-by-mobile station basis dependingupon the environment or condition of communications in the base stationor mobile station, whereby further improvement of throughput can beexpected independent of an access scheme (OFDM, MC-FDMA, etc.).Moreover, an effect of simplifying processing at the mobile station canbe expected by notifying the amount of information on scheduling, whichvaries with the maximum frequency block count, from the base station tothe mobile station.

Moreover, when switching the maximum frequency block count according to,for example, the CQI, an increase of PAPR can be prevented by reducingthe frequency block count in MC-FDMA, and therefore, an additionaleffect can be expected. In particular, PAPR is problematic in mobilestations having poor CQI, and accordingly, the maximum frequency blockcount is reduced to avoid an increase of PAPR. On the other hand, inmobile stations in which CQI is acceptable and PAPR is not significantlyproblematic, the maximum frequency block count may be set to a largervalue to aim at improvement of throughput from the multi-diversityeffect.

Furthermore, in a case that a frequency block count of one or more isused to perform transmission in MC-FDMA, the property of a CAZACsequence for use in a reference signal for use in demodulation of PUSCHis prevented from being deteriorated even in transmission using aplurality of frequency blocks by matching the CAZAC sequence for thereference signal to a transmit bandwidth of all frequency blocks. Thus,a PAPR property and channel quality measurement precision equivalent tothose for frequency block count=1 can be obtained.

While in the embodiments described above, a mode of allocating uplinkresource blocks and a mode of allocating downlink resource blocks havebeen individually described, a mode in which the mode of allocatinguplink resource blocks is combined with the mode of allocating downlinkresource blocks may be implemented.

Moreover, as obvious from the preceding description, while the mobilestation and base station in the present invention described above can beimplemented in hardware, it is possible to implement them by computerprograms.

Functions and operations similar to those in the embodiments describedabove are implemented by a processor running under programs stored in aprogram memory. It should be noted that part of functions in theembodiments described above may be implemented by computer programs.

The present invention is applicable generally to mobile wireless systemsthat perform resource block allocation.

1. A communication method implemented in a user equipment, thecommunication method comprising: receiving, from a base station,downlink control information for scheduling uplink resources; andtransmitting, to the base station, a demodulation reference signalgenerated using a sequence having a sequence length matching to atransmit bandwidth comprising the scheduled uplink resources, whereinthe transmit bandwidth comprises a plurality of sets of one or moreresource blocks, wherein each of the plurality sets of one or moreresource blocks comprises one or more consecutive resource blocks,wherein the plurality of sets of one or more resource blocks areseparated in frequency.
 2. The communication method according to claim1, wherein the sequence length is a number of all subcarriersconstituting the transmit bandwidth.
 3. The communication methodaccording to claim 1, wherein the demodulation reference signal is ademodulation reference signal associated with transmission of a physicaluplink shared channel.
 4. The communication method according to claim 1,wherein the information for scheduling uplink resources indicates astart position of a resource block for each set of one or more resourceblocks.
 5. The communication method according to claim 1, wherein theinformation for scheduling uplink resources indicates a start resourceblock for each set of one or more resource blocks.
 6. A communicationmethod implemented in a base station, the communication methodcomprising: transmitting, to a user equipment, downlink controlinformation for scheduling uplink resources; and receiving, from theuser equipment, a demodulation reference signal generated using asequence having a sequence length matching to a transmit bandwidthcomprising the scheduled uplink resources, wherein the transmitbandwidth comprises a plurality of sets of one or more resource blocks,wherein each of the plurality sets of one or more resource blockscomprises one or more consecutive resource blocks, wherein the pluralityof sets of one or more resource blocks are separated in frequency. 7.The communication method according to claim 6, wherein the sequencelength is a number of all subcarriers constituting the transmitbandwidth.
 8. The communication method according to claim 6, wherein thedemodulation reference signal is a demodulation reference signalassociated with transmission of a physical uplink shared channel.
 9. Thecommunication method according to claim 6, wherein the information forscheduling uplink resources indicates a start position of a resourceblock for each set of one or more resource blocks.
 10. The communicationmethod according to claim 6, wherein the information for schedulinguplink resources indicates a start resource block for each set of one ormore resource blocks.
 11. A user equipment comprising: a receiverconfigured to receive, from a base station, downlink control informationfor scheduling uplink resources; and a transmitter configured totransmit, to the base station, a demodulation reference signal generatedusing a sequence having a sequence length matching to a transmitbandwidth comprising the scheduled uplink resources, wherein thetransmit bandwidth comprises a plurality of sets of one or more resourceblocks, wherein each of the plurality sets of one or more resourceblocks comprises one or more consecutive resource blocks, wherein theplurality of sets of one or more resource blocks are separated infrequency.
 12. The user equipment according to claim 11, wherein thesequence length is a number of all subcarriers constituting the transmitbandwidth.
 13. The user equipment according to claim 11, wherein thedemodulation reference signal is a demodulation reference signalassociated with transmission of a physical uplink shared channel. 14.The user equipment according to claim 11, wherein the information forscheduling uplink resources indicates a start position of a resourceblock for each set of one or more resource blocks.
 15. The userequipment according to claim 11, wherein the information for schedulinguplink resources indicates a start resource block for each set of one ormore resource blocks.
 16. A base station comprising: a transmitterconfigured to transmit, to a user equipment, downlink controlinformation for scheduling uplink resources; and a receiver configuredto receive, from the user equipment, a demodulation reference signalgenerated using a sequence having a sequence length matching to atransmit bandwidth comprising the scheduled uplink resources, whereinthe transmit bandwidth comprises a plurality of sets of one or moreresource blocks, wherein each of the plurality sets of one or moreresource blocks comprises one or more consecutive resource blocks,wherein the plurality of sets of one or more resource blocks areseparated in frequency.
 17. The base station according to claim 16,wherein the sequence length is a number of all subcarriers constitutingthe transmit bandwidth.
 18. The base station according to claim 16,wherein the demodulation reference signal is a demodulation referencesignal associated with transmission of a physical uplink shared channel.19. The base station according to claim 16, wherein the information forscheduling uplink resources indicates a start position of a resourceblock for each set of one or more resource blocks.
 20. The base stationaccording to claim 16, wherein the information for scheduling uplinkresources indicates a start resource block for each set of one or moreresource blocks.